1. Field of the Invention
The present invention relates generally to vibration damping devices installed between components to be connected together in vibration isolating fashion, more particularly to a vibration damping devices suitably usable as an engine mount, a body mount or other mounts for use in automobiles.
2. Description of the Related Art
There have been widely used in a variety of fields vibration damping devices each having a rubber elastic body disposed between first and second mounting members fixable to components connected together in vibration isolating fashion. As one type of such vibration damping devices is known a vibration damping device including: a rubber elastic body of generally frustoconical configuration in its entirety; a first mounting member fixedly secured to a small-diameter side central portion of the rubber elastic body; and a second mounting member having a cylindrical portion that is secured to a large-diameter side outer circumferential surface of the rubber elastic body, thereby providing a construction wherein the first and second mounting members directly elastically connected to each other via the rubber elastic body (see JP-A-9-66721, for example).
The known vibration damping device is able to advantageously obtain a volume of the rubber elastic body, and to prevent excess strain induced in the rubber elastic body by restricting elastic deformation of the large-diameter outer circumferential surface of the rubber elastic body with the second mounting member attached thereon. In particular, the known vibration damping device is capable of advantageously exhibiting an enhanced anti-load performance as well as durability with respect to input load in a direction in which the small diameter end face and large diameter end face move toward each other. For the aforesaid advantages, the known vibration damping device has been examined to use as an engine mount or similar mounts adapted to bear initial or static load.
However, the conventional vibration damping device having the rubber elastic body of frustoconical shape inevitably suffers from tensile stress that is directly generated in the rubber elastic body when being subjected to input load in a rebound direction where the small and large diameter end faces move away from each other, i.e., in the opposite direction to the initial load input direction. As a result, the rubber elastic body is prone to suffer from cracks or other defects due to the input load in the rebound direction, leading to a likelihood of considerable deterioration in durability.